1. Field of the Invention
The present invention relates to a method and an apparatus for measuring the inclination angle of the free surface of a powdery or granular material stacked in a pile.
2. Description of the Prior Art
In general, in planning and designing a process for treating a powdery or granular material, in quality control of a powdery or granular material, or in a similar operation, it is essential to have a clear grasp of the flow and jet characteristics of the powdery or granular material treated. These characteristics are evaluated on the basis of various property values, such as the angle of repose and the spatula angle, that the powdery or granular material exhibits when it is stacked in a pile. Conventionally, the angle of repose and the spatula angle are measured by putting a protractor on the free surface of a pile of a powdery or granular material and reading the scale on the protractor.
However, in the measurement method described above, the protractor can be put in more than one way when the free surface of the pile of the powdery or granular material is uneven. This means that measurement results reflect how a measurer habitually conducts and evaluates the measurement, and therefore that different measurers often obtain different measurement results from the same measurement sample. In addition, determining the appropriate manner of putting the protractor is time-consuming, and thus the measurement as a whole requires an unduly long time.